These are the commercial jet engines you see, like the Boeing 777, 747, Airbus A330 and A380s. Though there is a considerable reduction of the engine thrust, at these altitudes the lower drag associated with low air density means a more economical flight with a higher True Air Speed.
Crepitus in the knees may be caused by knee injuries such as meniscus tears. These are fairly common in people who play sports, jog, or run. A meniscus tear can cause crepitus as the joint moves. Chondromalacia patella is a dull ache behind the kneecap, usually caused by overuse or injury. There will be damage to the undersurface cartilage covering the kneecap.
When the physician taps the patellar tendon with a hammer, this action causes the knee extensor muscle to stretch abruptly. This stretch activates the myotatic reflex, causing an extension of the lower leg. (Because the physician taps the tendon, this reflex is also referred to as the deep tendon reflex.ust as in the stretch reflex, the autogenic inhibition reflex must coordinate the activity of the extensor and flexor muscle groups (Figure 2.4). The Ib afferent fiber bifurcates in the spinal cord.